Lamp drive apparatus and drive method of a notebook computer

ABSTRACT

This present invention relates to a lamp drive apparatus and a drive method for an LCD equipped portable electronics to maintain a user-selected level of brightness in accordance with surrounding temperature of the lamp. In one operation mode a lamp drive apparatus reduces the current, which is applied into the lamp to maintain the already selected level of brightness in accordance with a detected lamp surrounding temperature where the brightness of the lamp has already been set in the LCD, to make the LCD device to illuminate no brighter than the selected level of brightness. Accordingly, the battery power can be used more efficiently or effectively. Thus, the battery life can be extended.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a lamp drive apparatus and drive method of portable electronics equipped with an LCD device, such as a notebook computer.

[0003] 2. Background of the Related Art

[0004] Portable electronics equipped with an LCD as a display device, like a notebook computer, use batteries more than AC input power, and require a backlight/front light lamp (hereinafter referred to as a lamp) to display contents on the LCD. For such a lamp, Cold Cathode Fluorescent Lamp (CCFL) is used the most.

[0005] In order to drive a CCFL lamp, necessary input conditions must be satisfied. Most portable electronics with a 14.1 inch or smaller LCD require 200˜700V (40˜150 KHz) of AC voltage and 0.5˜7 mA of lamp drive current. However, the brightness of the lamp is controlled by 0.5˜7 mA of lamp drive current.

[0006] In portable electronics, such as a notebook computer, an inverter is used as a power device that drives the lamp by applying appropriate lamp drive current into the lamp to control the brightness of the lamp in accordance with the lamp brightness control information. Further, the brightness of the lamp is in proportion to the size of the lamp drive current.

[0007] Generally, the lamp brightness control information uses a voltage level of 0˜5V. When assuming variable rate of 0.5V, minimum brightness at 0V and maximum brightness at 5V, the brightness levels can be defined into level 1 through level 11, where 1 mA is the lamp drive current of level 1, 1.5 mA is for level 2, 2 mA is for level 3, . . . , and 6 mA is the lamp drive current for level 11. In accordance with such brightness control information, the inverter is allowed to control the brightness of the lamp.

[0008] In addition, brightness of lamp changes also by surrounding temperature of lamp, and up to a certain point in temperature the brightness of the lamp changes in proportion to the surrounding temperature of the lamp. Thus, when the surrounding temperature of the lamp is at 25° C. and the standard brightness level at the 25° C. temperature is set at level 11 (5V), the inverter applies lamp drive current of 6 mA into the lamp to make the brightness of the lamp to be 150 Nit in accordance with the lamp light control information. However, if the surrounding temperature reaches 29° C., the inverter still applies lamp drive current of 6 mA into the lamp in accordance with the selected brightness level, and therefore, the brightness of the lamp increases to 170 Nit because of the 29° C. surrounding temperature of the lamp.

[0009] As described above, the related art lamp brightness control methods have various disadvantages. The related art lamp brightness control methods unconditionally apply current that corresponds with the selected level of brightness. Accordingly, the related art lamp brightness control methods waste power consumption in portable electronics such as a notebook computer that use batteries because the lamp illuminates unnecessarily brighter than an indicated brightness.

[0010] The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.

SUMMARY OF THE INVENTION

[0011] An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.

[0012] Another object of the present invention is to provide a lamp drive apparatus and a lamp drive method that maintain a brightness level of a light source for a LCD at a user selected brightness level.

[0013] Another object of the present invention to provide a lamp drive apparatus and lamp drive method of a portable computer that allows an effective use of a limited battery power to extend battery lifetime.

[0014] Another object of the present invention to provide a lamp drive apparatus and lamp drive method of a portable computer that allows an effective use of a limited battery power to extend battery lifetime by reducing lamp drive current to maintain a user-selected level of brightness after detecting the surrounding temperature of a lamp.

[0015] In order to achieve at least the above objects in a whole or in part and in accordance with the present invention, there is provided a lamp drive method of a portable computer that includes selecting a standard temperature of a lamp driving an LCD, selecting a brightness control level of a plurality of brightness control levels that determines a corresponding brightness in the LCD according to the standard temperature, detecting surrounding temperature of the lamp, selecting one of a first mode and a second mode for operating the lamp, wherein operating the lamp in the first mode includes reducing a drive current that is to be applied into the lamp to maintain the corresponding brightness within the plurality of brightness control levels in accordance with a change in the detected surrounding temperature of a lamp, and wherein operating the lamp in the second mode includes reducing brightness of the LCD in accordance with the change in detected surrounding temperature of the lamp to maintain a corresponding drive current of the selected brightness control level.

[0016] To further achieve the above objects in a whole or in part, in accordance with the present invention there is provided A lamp drive apparatus of a notebook computer, where brightness of a lamp has already been selected in an LCD device using the lamp as a light source of the LCD that includes a thermal sensor that detects a surrounding temperature of the lamp, a lamp drive unit that controls the brightness of the lamp by applying appropriate drive current into the lamp, and a brightness control unit that operates in one of a first mode and a second mode, wherein in the first mode the brightness control unit maintains the selected brightness within one of a corresponding plurality of brightness control levels in accordance with a change in the detected surrounding temperature of the lamp by reducing a drive current that is applied into the lamp.

[0017] To further achieve the above objects in a whole or in part, in accordance with the present invention there is provided a method of driving a lamp for an LCD of a portable computer that includes setting a default brightness in the LCD that corresponds to a prescribed value stored in the portable computer, checking a surrounding temperature of the LCD, selecting one of a first mode and a second mode for operating the lamp, wherein operating the lamp in the first mode includes receiving a user selected one of plurality of brightness control levels to set a first brightness and determining a corresponding first drive current as a drive current for the lamp, maintaining the first brightness within a first temperature range while the drive current varies to reduce lamp power consumption, determining a corresponding drive current at a minimum temperature of the first temperature range as a second drive current for a second temperature range that is below the first temperature range, and maintaining the second drive current while the temperature of the lamp is within the second temperature range to reduce the lamp power consumption, and wherein the operating the lamp in the second mode includes determining a third drive current that corresponds to the default brightness, maintaining the third drive current within a third temperature range while the brightness changes, determining a corresponding brightness level at a minimum temperature of the third temperature range to set a fourth brightness for a fourth temperature range that is below the third temperature range, and maintaining the fourth brightness while the temperature of the lamp is within the fourth temperature range while the drive current changes.

[0018] Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The invention will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein:

[0020]FIG. 1 is a block diagram illustrating a preferred embodiment of a lamp drive device in a portable computer in accordance with the present invention;

[0021]FIG. 2 is a flow chart illustrating a preferred embodiment of a method of operating a lamp drive device in a portable computer in accordance with the present invention; and

[0022]FIG. 3 to FIG. 5 are diagrams illustrating examples of a ROM table that relates to the brightness control information according to preferred embodiments of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0023]FIG. 1 is a block diagram that illustrates a preferred embodiment of a lamp drive device in a portable computer in accordance with the present invention. As shown in FIG. 1, a portable computer includes an LCD 50 as a displaying device, and a keyboard 10 for inputting key-inputs such as a brightness control key-input of a backlight or front light lamp that is the light source of the LCD 50. An inverter 40 is for controlling the lamp's brightness by applying appropriate drive current into the lamp, and a thermal sensor 20 is for detecting the lamp's surrounding temperature. A microcomputer 30 includes a keyboard controller 11 and ROM 31. The keyboard controller 11 is for recognizing the key inputs via the keyboard 10. The microcomputer 30 is for controlling the inverter 40 to control the lamp's brightness in accordance with the lamp brightness control information previously stored in the ROM 31 and controlling the inverter 40 to control the lamp's brightness in accordance with the brightness control information provided from the keyboard 10.

[0024]FIG. 2 is a flow chart illustrating a preferred embodiment of a method of operating a lamp drive device in a portable (e.g., personal or notebook) computer in accordance with the present invention. The preferred embodiment of the drive method of FIG. 2 can be used by the preferred embodiment of the lamp drive device of FIG. 1 and will be described with reference to FIG. 1, although the present invention is not intended to be so limited.

[0025] In the ROM 31, the brightness control information on the lamp's surrounding temperature is preferably stored in the form of a ROM table. Exemplary ROM tables are shown in FIGS. 3 to FIG. 5. As shown in FIGS. 3-5, such data was determined empirically.

[0026] The user-selected standard surrounding temperature (e.g., 25° C.) of the lamp (hereafter called a standard temperature) and the lamp's brightness (e.g., 150 Nit) are already assumed to be set in the microcomputer 30. Accordingly, as shown in FIG. 2, the microcomputer 30 is to take level 11 (e.g., =5V) as the standard brightness level with reference to the selected standard temperature and the selected lamp's brightness.

[0027] In such state, the user can select a lamp brightness maintaining mode via the keyboard 10. The lamp brightness maintaining mode maintains the lamp's brightness at the user-selected brightness of the lamp (e.g., 150 Nit) by reducing the drive current that is applied into the lamp. Preferably, the drive current is reduced each time a difference between the lamp's surrounding temperature and the selected standard temperature (e.g., 25° C.) is more than a prescribed interval (e.g., 2° C.) greater than the selected standard temperature.

[0028] Thus, as shown in FIG. 2, after a process starts, continuous detection of the lamp's surrounding temperatures is performed (step S10). The thermal sensor 20 is preferably placed adjacent to the LCD's 50 light source. When the brightness maintaining mode is not selected (step S20), the process preferably returns to monitor for such a selection at a later time. When the brightness maintaining mode is selected by the user (step S20), the microcomputer 30 preferably can display contents on the LCD 50 indicating that the lamp brightness maintaining mode has been selected. In addition, the microcomputer 30 preferably continuously compares the lamp's surrounding temperature M, which is detected by the thermal sensor 20, with the selected standard temperature (e.g., 25° C.) to check whether the difference (K) between the two temperatures is larger than the selected temperature by a fixed amount or value (e.g., T-25° C.=K>N, where N=2) (step S30).

[0029] According to the result (step S30), when the difference between the two temperatures is not larger than the selected temperature by the fixed amount (e.g., 2° C.), for instance, if the detected surrounding temperature T is at 26° C., the standard brightness level is applied (step S35). By letting the inverter 40 apply the lamp drive current corresponding with the standard brightness level (e.g., 5V) into the lamp, the microcomputer 30 then controls the lamp's brightness to correspond to the detected surrounding temperature and the standard brightness level (e.g., level 11) (step S36), with reference to the lamp's brightness control information stored in the ROM 31. If multiple brightness levels exist between a temperature range that is less than the fixed amount (e.g., 2° C. or N), the lamp brightness could be adjusted within the temperature range less than the fixed amount (step S36).

[0030] However, if the checked result (step S30) shows that the difference between the two temperatures is larger than the selected temperature by the fixed amount (e.g., 2° C.), compensation preferably occurs. For instance, if the detected surrounding temperature T is 29° C., then K is 4° C., which is larger than N. Since K is larger than N, the microcomputer 30 calculates a compensating coefficient C (step S31). The compensating coefficient C is preferably calculated from K-N, or in this example C=4-2 so that C gets 2. If the compensating coefficient is calculated in such a way, then the microcomputer 30 decreases the standard brightness level (e.g., level 11) by an amount of the calculated compensating coefficient, in this example, 2 (step S32). Alternatively, a brightness amount, or the like could be represented by the compensating coefficient as determined in step S31.

[0031] In addition, the microcomputer 30 checks the brightness control information that corresponds with the adjusted brightness level (e.g., level 9), which is preferably the voltage level, from the ROM 31. The checked voltage level becomes 4V in this example, and the microcomputer 30 provides the checked brightness control information of 4V to the inverter 40. Consequently, the microcomputer 30 controls the inverter 40 in accordance with the brightness control information so the inverter 40 applies the lamp drive current (e.g., in this example 5 mA), that corresponds with 4V, into the lamp (step S33). By reducing the lamp drive current in accordance with the detected surrounding temperature of lamp, the brightness of the lamp maintains the user-selected level of brightness of the lamp, in this example 150 Nit, to reduce power consumption (step S34). Preferably, the lamp's surrounding temperature is periodically or continuously checked so the process can be repeated. Thus, from step S34, control jumps back to step S10.

[0032] Until the lamp's brightness maintaining mode is off, the microcomputer 30 preferably continuously compares the lamp's surrounding temperature T, detected by the thermal sensor 20, with the selected standard temperature (e.g., 25° C). When the difference between the temperatures is different such as larger than the selected temperature by a fixed value (e.g., 2° C.), the microcomputer 30 reduces the lamp drive current to maintain the user-selected level of brightness of the lamp (e.g., 150 Nit).

[0033] As the temperature lowers or returns to the standard temperature (e.g., 25° C.), the microcomputer 30 preferably drives the inverter 40 using the values as determined above. As described above, the user-selected standard temperature and brightness level were already assumed to be set in the microcomputer 30 when the brightness maintaining mode was selected in the process of FIG. 2. However, the present invention is not intended to be so limited. For example, the standard temperature and brightness level can be preset in the system. Thus, the brightness maintaining mode reduces the drive current above the standard preset conditions according to temperature and the selected brightness level.

[0034] Preferably, below the standard temperature (e.g., 25° C.), the brightness maintaining mode maintains the corresponding lamp conditions of the initially selected conditions. As temperature decreases below the standard temperature, preferably the lamp drive current of the corresponding lamp conditions of the initially selected conditions is maintained to further reduce the drive current demands and extend a battery life of the portable computer in the brightness maintaining mode.

[0035] As described above, when a user did not select the lamp's brightness maintaining mode, the microcomputer 30 preferably is to control the lamp's level of brightness appropriately in accordance with the detected lamp's surrounding temperature T from the thermal sensor and the standard brightness level (i.e., level 11). For example, when the detected lamp's surrounding temperature is at 29° C., the microcomputer 30 is to check the brightness control information that corresponds with the selected brightness level (e.g, level 11). Therefore, the microcomputer 30 controls the inverter 40 according to the brightness control information to make the inverter 40 apply the lamp drive current (6 mA), that corresponds with 5V (e.g., level 11), into the lamp in order to control the lamp's brightness to 170 Nit in accordance with the lamp's surrounding temperature (e.g., 29°). The microcomputer 30 can control the level of brightness when the user did not select the brightness maintaining mode, for example, by calculating a compensating coefficient C. However, the level of brightness can be adjusted up from the level (e.g., level 9), that corresponds with the detected lamp's brightness, by preferably searching for the selected brightness of the lamp (150 Nit) from the table stored in the ROM 31, that corresponds with the detected lamp's surrounding temperature (for instance, 29° C.), and adjusting up by using the calculated compensating coefficient C.

[0036] Further, a user can manually control the brightness of the lamp, namely, the brightness of the LCD 50 by the keyboard 10 as described above. For example, a default value can be preset and the microcomputer 30 can increase the brightness of the lamp by a prescribed amount, for example, 10 Nit each time the user presses an increment-key from the keyboard 10. Whenever the user presses a decrement-key from the keyboard, the microcomputer 30 decreases the brightness of the lamp by the exemplary 10 Nit at a time.

[0037] As shown in FIG. 2, alternatively, should the condition in steps S20 and S30 fail, a standard brightness level could be applied using a corresponding lamp drive current and then be adjusted for the detected surrounding temperature of the lamp without the compensation performed in steps S31-S34.

[0038] As described above, preferred embodiments of a lamp drive apparatus and method have various advantages. Preferred embodiments of a lamp drive apparatus and the drive method of a notebook, or portable computer can extend the battery life by eliminating unnecessary use of battery power by controlling a LCD device to illuminate no brighter than the selected level of brightness.

[0039] The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. 

What is claimed is:
 1. A lamp drive method of a portable computer, comprising: selecting a standard temperature of a lamp driving an LCD; selecting a brightness control level of a plurality of brightness control levels that determines a corresponding brightness in the LCD according to the standard temperature; detecting surrounding temperature of the lamp; selecting one of a first mode and a second mode for operating the lamp, wherein operating the lamp in the first mode comprises, reducing a drive current that is to be applied into the lamp to maintain the corresponding brightness within the plurality of brightness control levels in accordance with a change in the detected surrounding temperature of a lamp, and wherein operating the lamp in the second mode comprises, reducing brightness of the LCD in accordance with the change in detected surrounding temperature of the lamp to maintain a corresponding drive current of the selected brightness control level.
 2. The lamp drive method of claim 1, wherein said reducing a drive current reduces the drive current applied into the lamp in the first mode to maintain the corresponding brightness when a difference between the detected surrounding temperature of the lamp and the selected standard temperature of the lamp is greater than a fixed value.
 3. The lamp drive method of claim 2, comprising determining and storing an empirical relationship between temperature and the brightness at the plurality of brightness control levels for each of a plurality of temperatures above the standard temperature for the lamp.
 4. The lamp drive method of claim 3, wherein the corresponding drive current sets a maximum power use rate of the LCD drive.
 5. The lamp drive method of claim 1, wherein the selecting a brightness control level sets a voltage level of a plurality of voltage levels.
 6. The lamp drive method of claim 1, wherein said reducing steps are to be operated in accordance with a lamp brightness maintaining mode chosen by a user.
 7. The lamp drive method of claim 6, wherein a battery life of a battery of the portable computer is extended in the lamp brightness maintaining mode.
 8. A lamp drive apparatus of a notebook computer, where brightness of a lamp has already been selected in an LCD device using the lamp as a light source of the LCD, comprising: a thermal sensor that detects a surrounding temperature of the lamp; a lamp drive unit that controls the brightness of the lamp by applying appropriate drive current into the lamp; and a brightness control unit that operates in one of a first mode and a second mode, wherein in the first mode the brightness control unit maintains the selected brightness within one of a corresponding plurality of brightness control levels in accordance with a change in the detected surrounding temperature of the lamp by reducing a drive current that is applied into the lamp.
 9. The lamp drive apparatus of claim 8, wherein said brightness control unit reduces the drive current that is to be applied into the lamp in the first mode to maintain the selected brightness when a difference between the detected surrounding temperature of the lamp and a selected standard temperature of the lamp is greater than a fixed amount.
 10. The lamp drive apparatus of claim 9, wherein the selected brightness is determined at the standard temperature.
 11. The lamp drive apparatus of claim 10, wherein in the second mode the brightness control unit reduces brightness of the LCD in accordance with the change in the detected surrounding temperature of the lamp to maintain a corresponding drive current selected at the standard temperature.
 12. The lamp drive apparatus of claim 11, further comprising an input unit that receives inputs including a mode selection, wherein said brightness control unit controls said lamp drive unit in the first and second modes in accordance with selection of a brightness maintaining mode from a user through the mode selection received by said input unit.
 13. The lamp drive apparatus of claim 8, further comprising a memory that stores brightness control information including lamp drive current in accordance with the brightness of the lamp, wherein said brightness control unit controls said lamp drive unit in accordance with the brightness control information.
 14. A method of driving a lamp for an LCD of a portable computer, comprising: setting a default brightness in the LCD that corresponds to a prescribed value stored in the portable computer; checking a surrounding temperature of the LCD; selecting one of a first mode and a second mode for operating the lamp, wherein operating the lamp in the first mode comprises, receiving a user selected one of plurality of brightness control levels to set a first brightness and determining a corresponding first drive current as a drive current for the lamp, maintaining the first brightness within a first temperature range while the drive current varies to reduce lamp power consumption, determining a corresponding drive current at a minimum temperature of the first temperature range as a second drive current for a second temperature range that is below the first temperature range, and maintaining the second drive current while the temperature of the lamp is within the second temperature range to reduce the lamp power consumption, and wherein the operating the lamp in the second mode comprises, determining a third drive current that corresponds to the default brightness, maintaining the third drive current within a third temperature range while the brightness changes, determining a corresponding brightness level at a minimum temperature of the third temperature range to set a fourth brightness for a fourth temperature range that is below the third temperature range, and maintaining the fourth brightness while the temperature of the lamp is within the fourth temperature range while the drive current changes.
 15. The method of claim 14, wherein said one of the first and second modes is determined by a user action at the portable computer.
 16. The method of claim 15, wherein the first mode is a power saving mode, and wherein in the second temperature range the brightness changes.
 17. The method of claim 14, wherein the first and third temperature ranges are equal, and wherein the second and fourth temperature ranges are equal.
 18. The method of claim 14, wherein the first mode is a brightness maintaining mode. 